Means for equalizing transmission over lines of different electrical characteristics



June 19, 1923.

L F. MOREHOUSE MEANS FOR EQUALIZING TRANSMISSION OVER L ELECTRICAL CHARACTERISTICS Filed 06%. 29 1918 l AS8388 INES OF DIFFERENT LEJI I N V EN TOR. aiefiause F fafac.

ATTORNEY Patented June 19, 1923.

LYMAN F. MOREHOUSE, or MONTCLAIR, NEW JERSEY, assrenon TO AMERICAN TELE- PHONE AND TELEGRAPH company, A CORPORATION or NEW YORK.

MEANS FOR EQUALIZING TRANSMISSION OVER LINES OF IDIFFEBENT ELECTRICAL CHARACTERISTICS.

Application filed October 29, 1918. Serial No. 260,155.

To all whom it may concem:

Be it known that I, LYMAN F. MoRnHoUsn, residing at 'Montclair, in the county of Essex and State of N ew'J ersey, have invented certain Improvements in Means for Equalizing' Transmission Over Lines of Different Electrical Characteristics, of whichthe following is a specification.

This invention relates to telephone systems and more particularly to the provision of means whereby the transmission over telephone lines of different electrical characteristics may be equalized or rendered more uniform.

Telephone lines have, in general, different electrical characteristics varying with the length of the lines. For any particular type of line construction which may be employed the resistance, capacity, induc tance and leakage of the circuit increase-.1

with the length. These variations in-the electrical characteristics of the different subscribers lines in a telephone system introduce a number of variable effects in the telephone service rendered from different stations. trical characteristics :result in different degrees of attenuation in the alternating tele phone current passing over the subscribers small communities, the resistance ofthe line causes a further effecton the transmission in that it reduces the amount of direct current which the transmitter receives from the central oflice battery and so renders itless efficient in the generation of the alternating telephone current;

In view of the conditions above referred to, it hasv not been. heretoforepossible to For example, the different elec-v lines and thus give louder and more efiect'ive.

tems now so generally employed invall but:

diaphragm of the trans-nutter, said coil being so'related to the transmission line that the current supplied to the granular carbon resistance button of the transmitter will energize said coil. Bymeans of this arrangement damping of the diaphragm due to the action of the coil will increase with the increase in the current supplied over the line and by properly proportioning the coil and relating it to the diaphragm a practically uniform grade of transmission may be secured for loops of all reasonable lengths.

The invention may now be fully understood' from-the following description when read in connection with the accompanying drawin view 0 a transmitter embodying the principles of the invention, Figure '2 is a circuit diagram of'a transmission line provided with a transmitter of the type shown Iin Figure 1, Figure 3 is a sectional view of amodified form oftransmitter and Figure 6L 1s a'circuitdlagram of a transmission line employing a transmitter of the typeshown in Figure 3. v

Referring to Figure 1, a telephone transmitter is shown comprising the usual front casing 1, back'casing or shellQ, mouth piece 3, supporting bridge 4 and diaphragm 5. Suitably mounted upon thef supporting bridge 4 is a granular carbon resistance button 6 of a Well known type comprising a back'electrode 7 and a front electrode 8 between which is placed a suitable amount of granulated carbon, said front electrode 8 inwhich Figure l is asectio'na'l being carried by and movablewith the dia phragm 5. Also mounted uponthe supporting bridge 4 is a two-pole electromagnetic'structur'e comprising :pole pieces 9 and '10 secured to the bridge by means of'screws,

said pole pieces having their ends bent at right angles as shown at 11 and 12in order that the faces ofthe pole pieces may'lie closely to the diaphragm in the region of the resistance button- 6. These pole pieces carry coils 13and 14.- through which the current supply for the transmitter flows. The magnetic circuit is completed through the bridge 4.

The circuit connections of the transmitter of Figure 1 are shown in Figure 2 in which is shown a transmission line L provided with a source of supply current'B at the central oflice and terminating at the subscribers station in a substation arrangement comprising the usual receiver R, ringer 15 and induction coil 16. From one terminal 17 of the line L, a series connection extends through the windings 14 aiid13 in'seri'es'a'iid thence through the granular carbon'button 6 to the diaphragm. From the diaphragm a connection extends through one winding of the induction coil 16 to the terminal 18 of the line L. It will thus be seen that the current supply vfrom source B flows over'tlie line and through the coils 13 and 14 in series with the resistance button 6, so that the increased eiliciency of the transmitter which would normally-result fronithelarge current supply on short lines will be'overcome bythe dam-ping of the diaphragm due to the action of the coils 13 and 1 1. The damping is effected by eddy currents set up in the l diaphragm due to its Vibration in the magnetic field produced by the direct current through coils 13 and 14, and to the alternating flux set up bythe coils as the result of changes in thetransmitter resistance. The magnitude of the direct and alternating fluxes are proportional .to the amount of current flowing through the coils and hence the damp ng will increase as. the current ,in-

creases with decreasing lengths of loop. In

order to prevent transmission lossdue to the impedance of the magnetic coils,-th'ey may be shunted bya non-inductive resista'nce19 or av condenser 20, or both. By this arrangem'ent also currentyariationsproduced bythe resistance button .6 will pass through the shunt circuit, including the noninductive resistance 19, or condenser 20,-without actuating the ,coils 13 and 151, so that singing will not result. A modified arrangement. ofthe transmitter is illustrated 'in l igure 3, like parts being indicated by the same reference characters. This arrangement differs from that of Figure 1 in that a single pole magnetic structure surrounds the granular carbon resistance button 6. The pole piece 21 of this magnet is cylindricalin shape and is mounted on the body of the resistance button 6, being secured in place by means of a 'set screw 22. Adjacent the diaphragm 5 the pole piece 21 is provided with a right angular extension 23 lying parallel to the diaphragm in the vicinity of the mounting of the movable electrode 8. The cylindrical pole piece 21 is surrounded by a coil24 which, as shown in the diagram of Figure 4,,is connected; in series with the resistance button 6, the circuit extending from the termany minal 17 of the line L through the winding of coil 24, through the button 6, to the diain Figure 2 the coil 24' is shunted by a nonind'u'ctive resistance 19, or a condenser 20, or both. The diaphragm 5 may be of either magnetic or nonmagnetic material and the action will be the same as that described in connection with Figures 1 and 2.

It will be seen that by means of the arrangements above described a simple yet efiicient'means has-been provided whereby the telephonic transmission over lines of difierent character may be equalized'and rendered more uniform so that'subscribers having instrumentson loops of different length will receive substantially the same transmission.

It will also be obvious that the general 'prin- F ciples herein disclosed may be embodied in other organizations widely diiferent from those illustrated without departing from the spirit of the invention'as defined in the following claims.

What is claimed is: p

1. In aasignaling system, transmission lines of different electricalcharacteristics, telephone transmitters for each line, a common source of current supply for said trans-- mitters, and means associated With said transmitters-to automatically vary the efficiency thereof in accordance with the current supplied thereto.

2. In a signaling system, transmission lines of different electrical characteristics, telephone transmitters for each line, common source of current supply for said transmitters, and means associated with said 'transinitters'i and operating automatically to causetransmitters receiving small current supply to 'generate relatively greater talking currents than transmitters receiving larger current supply.

3. In 'a signalingf system, transmission lines of different electrical characteristics, telephone transmitters for each line, a common source of current supply for said'transinitters, diaphragms for said transmitters, means for; damping said diaphragms'so that the damping thereof will'a'utomaticall vary in accordance with the currentsuppiied to said transmitters.

a. In a si'gnalin' system, transmission lines of different e ectrica'l' characteristics, telephone transmitters for each line, a common source of current supply for said 'transmitt'ers, diaphragms for, said transmitters, means for damping said diaphragms so that the damping will automatically beadjusted to become greater for transmitters receiving larger current supply than for transmitters receiving small current supply.

5. In a, signaling system, transmission lines of difl'erent electrical characteristics,

telephone transmitters for each line, a common source of current supply for said transmitters, diaphragms for said transmitters, electromagnetic means for damping each transmitter, said electromagnetic means being included in circuit with said source of current supply to automatically adjust the damping of each transmitter diaphragm in accordance with the current supplied to the transmitter.

6. In a signalin system, transmission lines of different e ectrical characteristics, telephone transmitters for each line, a common source of current supply for said transmitters, diaphragms for said transmitters, electromagnetic means for damping each transmitter, said electromagnetic means being included in circuit with said source of current supply in such manner that the dia-' phragms of transmitters receiving a large current supply will be automatically damped more than those of transmitters receiving a small current supply.

7. In a signaling system, transmission lines of different electrical characteristics, telephone transmitters for each line, a common source of curent supply for said transmitters, diaphragms for said transmitters, electromagnetic coils in magnetic relation to each of said diaphragms, said coils being in series with said transmitters so that the damping of each diaphragm will automatically vary with the current supplied to the transmitter.

8. In a signaling system, transmission lines of difierent electrical characteristics,

telephone transmitters for each line, a com mon source of current supply for said transmitters, diaphragms for said transmitters, electromagnetic coils in magnetic relation to each of said diaphragms, said coils being,

9. In a signaling system, a transmission line, a telephone transmitter, a source of current supply for said transmitter, said transmitter comprising a resistance button and a diaphragm, an electromagnetic coil in magnetic relation with said diaphragm, said coil being in series circuit with saidrresistance button with respect to said source of current supply, and a by-pass circuit, in

shunt with said coil to prevent transmission losses due to the impedance of said coil at the frequencies of voice currents.

In testimony whereof, I have signed my name to this specification this twenty eighth day of October, 1918.

LYMAN F. MOREHOUSE. 

